Polyesters are commercially available and are widely used in a variety of applications such as magnetic tapes, packaging, capacitors, industrial belting, protective coatings, structural adhesives and composite matrices. There are basically three classes of polyester: amorphous thermoplastics, crystalline or semi-crystalline materials, and unsaturated or crosslinked polymers. Each class of polyesters has a unique set of properties. The synthesis of polyesters is amenable to tailor a material for a particular application. A tremendous amount of work has been reported on polyesters and excellent reviews are available, e.g., I. Goodman "Polyesters," in Encyclopedia of Polymer Science and Technology Vol. 11, p. 62 (1969), edited by H. F. Mark and N. G. Gaylord; H. V. Boenig "Unsaturated Polyesters," Ibid., Vol. 11, p. 129 (1969); and P. W. Morgan "Condensation Polymers," Chapter on Polyesters, p. 325, Interscience Publishers, New York (1965).
The amorphous polyesters of the prior art are sensitive to certain solvents especially in a stressed condition and, upon exposure, undergo solvent induced stress crazing and cracking. The crystalline polyesters have better solvent resistance than the amorphous materials but are generally more difficult to process. In addition, the degree of crystallinity in the polymer influences the properties and in many instance, the degree of crystallinity cannot be controlled, especially when processed as adhesives or composite matrices. The crosslinked polyesters undergo pronounced shrinkage upon cure which results in built-in stresses. In addition, these crosslinked polyesters are generally brittle materials and cannot be thermoformed. The materials of this invention exhibit improved solvent resistance, higher use temperature, good toughness, and thermoformability and thereby overcome the disadvantages of the prior art.
It is therefore an object of the present invention to provide a novel method for preparing ethynyl-terminated polyesters.
Another object of the present invention is to provide a new composition of matter comprised of ethynyl-terminated ester oligomers and polymers.
A further object of the present invention is to provide novel cured resins in the form of films, coatings, adhesives and composite matrices produced from cured ethynyl-terminated polyesters.
An additional object of the present invention is to provide polymers having improved solvent resistance and use temperature properties.
Another object of the present invention is to provide a process for preparing thermoplastic polyesters having improved solvent resistance and use temperatures without compromising the advantageous thermoformability and toughness property characteristics thereof.
A further object of the present invention is a process for preparing controlled density thermoplastic polyesters to thereby influence the physical properties of the cured material.